Generally, a piece of rack-mounted equipment is mounted to a rack by a pair of slide rail assemblies. For example, US Patent Publication No. 2014/0104777 A1 discloses a rail adapter for tool-less coupling to a rack. The adapter is coupled to a rail in order to mount the rail to a rack. More specifically, the adapter (32) is mounted on a mount (28) of the rail (16). The adapter (32) also has a latch (38) as shown in FIG. 5 and FIG. 6 accompanying the specification of the afore-cited patent application. The rail (16) is mounted to a plurality of openings (26) of the rack (12) via the latch (38) and a support (36). As the openings may vary in shape and size from one rack to another, it is highly desirable to have a medium member or device that enables a rail to cope with racks of different specifications as much as possible.